1. Field of the Invention
The present invention relates to a device that is interposingly used in a liquid transporting pipe through which transported liquid such as liquid for processing a semi-conductor device is transported to various portions by a reciprocal pump, to damp pulsations generated by variations in flow quantity and pressure due to the reciprocal operation of the reciprocal pump.
2. Description of the Prior Art
A pulsation damping device of this kind is disclosed in, for example, Japanese Patent Application Laying-Open Nos. 617752 and 8-159016.
Among such disclosed devices, the pulsation damping device for a pump which is disclosed in Japanese Patent Application Laying-Open No. 6-17752 is shown in FIG. 11. The device comprises: a sealed device body casing 60; a liquid chamber 61a which is disposed in the device body casing 60, which temporarily stores liquid transported by a reciprocal pump to exert a liquid storage function, and which then allows the liquid to flow out; and an air chamber 61b which is disposed in the device body casing 60 and separated from the liquid chamber 61a via a pulsation suppression diaphragm 62 that is configured by an extendable and contractible bellows, and which is filled with compressed air. The device is configured so that the pulsation suppression diaphragm 62 is extended and contracted by pulsations due to the discharge pressure of the pump, and the pulsations are damped by the capacity change of the liquid chamber 61a. 
In the case where the discharge pressure of the reciprocal pump is varied, the extension and contraction amount of the pulsation suppression diaphragm 62 must be restricted to a predetermined range in order to balance the liquid pressure in the liquid chamber 61a with the air pressure in the air chamber 61b. To comply with this, the following configuration is employed in the device shown in FIG. 11. An automatic air supply valve mechanism 63 and an automatic air discharge valve mechanism 64 are disposed in the device body casing 60. In the case where the pulsation suppression diaphragm 62 is extended from a reference value S in the direction of increasing the capacity of the liquid chamber by the liquid pressure variation in the liquid chamber 61a, when the diaphragm exceeds a predetermined range A, an air supply port 66 is opened by the pulsation suppression diaphragm 62 via a valve push rod 65 of the automatic air supply valve mechanism 63, to adjust the air filling pressure of the air chamber 61b so as to raise the pressure. In the case where the pulsation suppression diaphragm 62 is contracted from the reference value S in the direction of decreasing the capacity of the liquid chamber, when the diaphragm exceeds a predetermined range B, an air discharge port 68 is opened by the automatic air discharge valve mechanism 64 by means of a slider 67 which abuts against a closed end face 62a of the pulsation suppression diaphragm 62, to discharge the air in the air chamber 61b so as to lower the air filling pressure.
By contrast, FIG. 12A shows the pulsation damping device for a pump which is disclosed in Japanese Patent Application Laying-Open No. 8-159016, and FIG. 12B shows an air supply/discharge switch valve mechanism for the pump. The device uses an air chamber internal pressure adjust valve mechanism which restricts the capacity change of a liquid chamber 61a that is disposed in a similar manner as the liquid chamber 61a disclosed in Japanese Patent Application Laying-Open No. 6-17752, within a predetermined range. In the mechanism, the air supply/discharge switch valve mechanism comprising: an operating rod 69 which operates in accordance with the displacement of the closed end face 62a of the pulsation suppression diaphragm 62; and a slide valve element 71 which is operated by the operating rod 69 to cause an air supply and discharge passage 70 connected to the air chamber 61b to selectively communicate with the air supply port 66 and the air discharge port 68 is protrudingly attached to the outside of the device body casing 60. The valve mechanism is configured so that, when the capacity of the liquid chamber 61a is increased to exceed a predetermined range, the air supply port 66 communicates with the air supply and discharge passage 70, and, when the capacity of the liquid chamber 61a is decreased to exceed the predetermined range, the air discharge port 68 communicates with the air supply and discharge passage 70. The valve mechanism comprises: a cylindrical casing 72 in which the air supply port 66, the air discharge port 68, and the air supply and discharge passage 70 communicating with the air chamber 61b are formed; and the slide valve element 71 which is coaxially connected to the operating rod 69, and which is slidably fitted into a cylinder 73 housed in the cylindrical casing 72.
Among the above-mentioned two conventional art examples, in the former pulsation damping device disclosed in Japanese Patent Application Laying-Open No. 6-17752, as shown in FIG. 11, the automatic air supply valve mechanism 63 and the automatic air discharge valve mechanism 64 are disposed integrally with a lower end member 60a constituting a part of the device body casing 60. When one of the valve mechanisms 63 and 64 is broken or becomes faulty, therefore, the whole device must be disassembled and repaired, or replaced with another one. In any case, the work requires much labor. Therefore, the configuration is disadvantageous in maintenance and cost. Furthermore, the device has a structure in which the air discharge port 68 of the automatic air discharge valve mechanism 64 is closed by a gravitational drop of a discharge valve element 75. Therefore, the closing operation is unstable, and the device must be always placed so that the discharge valve element 75 in a vertical posture and the air discharge port 68 maintain their vertical positional relationship. For example, the device cannot be applied to a use in which the discharge valve element 75 has a horizontal posture, and hence the kinds of devices are restricted. Moreover, the valve push rod 65 of the automatic air supply valve mechanism 63, and the slider 67 of the automatic air discharge valve mechanism 64 which are independently juxtaposed are in direct contact at two points with the closed end face 62a of the pulsation suppression diaphragm 62 configured by the bellows. One of the members, or the valve push rod 65 is in direct contact with a position which is deviated from the center portion of the closed end face 62a. When the pulsation suppression diaphragm 62 is extended and contracted, therefore, an offset load is applied to the diaphragm, thereby hindering the extendable and contractible portion of the pulsation suppression diaphragm 62 from being straightly deformed extendingly and contractingly in the axial direction Xxe2x80x94X of the device body casing 60. This impairs the response property of the automatic air supply and discharge valve mechanisms 63 and 64, thereby causing the pulsation suppressing performance to be lowered.
In the air supply/discharge switch valve mechanism disclosed in the latter publication or Japanese Patent Application Laying-Open No. 8-159016, the configuration in which suction and discharge of air are concentrated into the single valve mechanism as shown in FIGS. 12A and 12B is employed. Even when the valve mechanism is broken or becomes faulty, therefore, it is not required to disassemble the whole device, and repair and replacement can be performed by detaching only the single air supply/discharge switch valve mechanism. Unlike the former device, the closing of the air supply and discharge ports 66 and 68 is not performed by the weight of the discharge valve element 75. Therefore, the problem of the former device can be solved. By contrast, however, the device has drawbacks that the air supply/discharge switch valve mechanism itself is complicatedly structured, that it is difficult to seal the slide valve element 71, and that the mechanism protrudes to the outside of the device body casing 60 to increase the size of the whole device, thereby making the device bulky.
The invention has been conducted in view of the above-discussed problems. It is an object of the invention to provide a pulsation damping device which can be placed and used in either of the vertical and horizontal directions, and which can be configured in a wide variety of kinds.
It is another object of the invention to provide a pulsation damping device in which maintenance of air supply and discharge valves can be easily conducted, and an air supply/discharge valve structure wherein the air supply valve and the air discharge valve are separately and independently juxtaposed is employed so that the valve structure can be more simplified, the fault frequency can be made lower, and the device can be produced more economically than the above-mentioned air supply/discharge switch valve mechanism.
It is a further object of the invention to provide a pulsation damping device in which an offset load on a pulsation suppression diaphragm configured by a bellows is eliminated while an air supply valve and an air discharge valve are separately and independently juxtaposed, and an extendable and contractible portion of the pulsation suppression diaphragm is always caused to be straightly deformed extendingly and contractingly in the axial direction of a device body casing, whereby the response property of the opening and closing operations of the air supply and discharge valves can be improved and the pulsation suppressing performance can be ensured.
The pulsation damping device of the invention will be described with reference to the accompanying drawings. The reference numerals in the figures are used in this paragraph in order to facilitate the understanding of the invention, and the use of the reference numerals is not intended to restrict the contents of the invention to the illustrated embodiments.
The invention provides a pulsation damping device comprising: a sealed device body casing 17 having a liquid chamber 20a which receives liquid to be transported by a reciprocal pump or the like through an inflow passage 2, which temporarily stores the liquid, and which then allows the liquid to flow out through an outflow passage 3, and an air chamber 20b which is to be filled with compressed air for suppressing pulsation; and a pulsation suppression diaphragm 18 which is disposed in the device body casing to separate the liquid chamber 20a and the air chamber 20b from each other, and which is freely extended and contracted in accordance with a balance between variations in flow quantity and pressure of the transported liquid flowing into the liquid chamber, and an air filling pressure of the air chamber, wherein the pulsation damping device includes: a valve casing 23 which is placed in the air chamber 20b to be opposed to a center portion of a closed end face of the pulsation suppression diaphragm 18, the closed end face facing the air chamber 20b, and which has an air supply port 31 through which, when the air filling pressure of the air chamber is to be raised, the compressed air is introduced into the air chamber, and an air discharge port 32 through which, when the air filling pressure of the air chamber is to be lowered, the compressed air is discharged from the air chamber to an outside; an air supply valve 36 which is disposed in the valve casing, and which opens and closes the air supply port 31; a spring 37 which always closingly urges the air supply valve; an air discharge valve 43 which is disposed in the valve casing 23 to be juxtaposed with the air supply valve 36, and which opens and closes the air discharge port 32; a spring 49 which always closingly urges the air discharge valve; an air supply/discharge valve control plate 28 which is placed to abut against the center portion of the closed end face of the pulsation suppression diaphragm 18; an air supply valve rod pressing portion 55 which is disposed on the air supply/discharge valve control plate, and which pushes a rear end portion of a valve rod 41 of the air supply valve 36 to open the air supply valve, in accordance with that the liquid pressure of the liquid chamber is raised to overcome the air pressure of the air chamber and the pulsation suppression diaphragm 18 is extended; an air discharge valve rod pulling portion 56 which is juxtaposed with the air supply valve rod pressing portion on the air supply/discharge valve control plate 28, which is slidably connected to a rear end portion of a valve rod 45 of the air discharge valve 43, and which pulls the valve rod 45 to open the air discharge valve 43, in accordance with that the liquid pressure of the liquid chamber is lowered, the air pressure of the air chamber overcomes the liquid pressure of the liquid chamber, and the pulsation suppression diaphragm 18 is contracted; and springs 57 which are interposed between the valve casing 23 and the air supply/discharge valve control plate 28 to respectively surround outer peripheries of the air supply valve rod 41 and the air discharge valve rod 45, and which pressingly urge the air supply/discharge valve control plate 28 toward the center portion of the closed end face of the pulsation suppression diaphragm 18.
In this case, the valve casing 23 and the air supply/discharge valve control plate 28 may be connected to each other by one, or more preferably plural guide shafts 58 which are parallel to extending and contracting directions of the pulsation suppression diaphragm 18, and the air supply/discharge valve control plate 28 may be moved in parallel along the guide shafts.
In the thus configured pulsation damping device, in accordance with that the liquid pressure of the liquid chamber 20a is raised to overcome the air pressure of the air chamber 20b and the pulsation suppression diaphragm 18 is extended, the air supply valve rod pressing-portion 55 on the air supply/discharge valve control plate 28 pushes the rear end portion of the air supply valve rod 41 to open the air supply valve 36, thereby supplying the air into the air chamber 20b. When the liquid pressure of the liquid chamber 20a balances with the air pressure of the air chamber as a result of the above operation, the pulsation suppression diaphragm 18 is contracted, and the air supply valve 36 is closed by the forces of the spring 37 and the air pressure.
In accordance with that the liquid pressure of the liquid chamber 20a is lowered, the air pressure of the air chamber 20b overcomes the liquid pressure of the liquid chamber, and the pulsation suppression diaphragm 18 is contracted, the air discharge valve rod pulling portion 56 on the air supply/discharge valve control plate 28 pulls the air discharge valve rod 45 to open the air discharge valve 43, thereby discharging the air in the air chamber 20b. When the liquid pressure of the liquid chamber 20a balances with the air pressure of the air chamber 20b as a result of the above operation, the pulsation suppression diaphragm 18 is extended, and the air discharge valve 43 is closed by the forces of the air pressure and the spring 49. Irrespective of variations of the discharge pressure of a reciprocal pump or the like which transports the transported liquid to the liquid chamber 20a, therefore, the extension and contraction amount of the pulsation suppression diaphragm 18 can be restricted within a predetermined range, and the pulsation amplitude can be suppressed to a low level.
Since the air supply and discharge valves 36 and 43 are respectively closingly urged by the functions of the springs 37 and 49, the air supply port 31 and the air discharge port 32 can be closed stably and surely. Even when the device is placed and used in any of the vertical and horizontal directions so that the air supply valve 36 and the air discharge valve 43 have a vertical or horizontal posture, the opening and closing operations of the air supply port 31 and the air discharge port 32 are not hindered.
Although the air supply valve 36 and the air discharge valve 43 are independently juxtaposed in the valve casing 23, the air supply valve rod pressing portion 55 for opening the air supply valve 36, and the air discharge valve rod pulling portion 56 for opening the air discharge valve 43 abut against the center portion of the closed end face of the pulsation suppression diaphragm 18 via the air supply/discharge valve control plate 28. In extension and contraction of the pulsation suppression diaphragm 18, therefore, an offset load is eliminated, so that the extendable and contractible portion of the pulsation suppression diaphragm 18 is always straightly deformed extendingly and contractingly in the axial direction of the device body casing 17. Consequently, the response property of the opening and closing operations of the air supply and discharge valves 36 and 43 is improved and the pulsation suppressing performance can be ensured.
In this case, when the valve casing 23 and the air supply/discharge valve control plate 28 are connected to each other by one, or more preferably plural guide shafts 58 which are parallel to extending and contracting directions of the pulsation suppression diaphragm 18, the air supply/discharge valve control plate 28 can be always surely moved in parallel, and the operations in which the extendable and contractible portion of the pulsation suppression diaphragm 18 is always straightly deformed extendingly and contractingly in the axial direction of the device body casing 17 can be further ensured.
In another pulsation damping device of the invention, the valve casing 23 is detachably fittingly attached to the device body casing 17. According to this configuration, when one of the air supply valve 36 and the air discharge valve 43 is broken or becomes faulty, repair and replacement of the valve can be easily performed by detaching only the valve casing 23 from the device body casing 17. This is advantageous in maintenance. Furthermore, the air supply valve 36 and the air discharge valve 43 are separately and independently disposed in the single valve casing 23. Therefore, the valve structure is simple, becomes less faulty, and can be economically produced, and the valve casing 23 can be compactly accommodated without substantially protruding to the outside of the device body casing 17.
In a further pulsation damping device of the invention, an air driven reciprocal pump portion 4 is integrally attached to the device body casing 17, the reciprocal pump portion 4 comprises: a pump casing 6 which is disposed integrally with one side portion of the device body casing 17; a pump diaphragm 7 which is disposed in the pump casing 6 to be opposed to the pulsation suppression diaphragm 18, and which is extendingly and contractingly deformable in the extending and contracting directions of the pulsation suppression diaphragm 18; an air cylinder portion 14 which drives the pump diaphragm 7 to extend and contract the diaphragm; and a pump working chamber 9a in which check valves 16a and 16b are disposed inside the pump diaphragm 7, the check valves being alternately opened and closed in accordance with extending and contracting deformation of the pump diaphragm to perform actions of sucking and discharging the liquid, and the transported liquid which is discharged from the pump working chamber 9a via the discharge check valve 16b is temporarily sent into the liquid chamber 20a. 
In the thus configured pulsation damping device, when the pump diaphragm 7 is extendingly and contractingly deformed via the air cylinder portion 14, the suction check valve 16a and the discharge check valve 16b in the pump working chamber 9a are alternately opened and closed, and suction of the transported liquid from the inflow passage 2 into the pump working chamber 9a, and discharge of the transported liquid from the pump working chamber 9a to the outflow passage 3 are repeated to perform a predetermined pumping function. At this time, the transported liquid which is discharged from the pump working chamber 9a via the discharge check valve 16b flows out into the outflow passage 3 through the liquid chamber 20a of the pulsation damping device 5. In this case, in a peak portion of pulsations of the discharge pressure of the discharged liquid, the pulsation suppression diaphragm 18 is moved in the direction along which the capacity of the liquid chamber is increased to absorb the pressure, and, in a valley portion of the pulsations, the pulsation suppression diaphragm 18 is moved in the direction along which the capacity of the liquid chamber is decreased to raise the pressure of the discharged liquid, thereby absorbing pulsations. As a result, the transported liquid can be flown out continuously and smoothly without producing pulsations. Since the reciprocal pump portion 4 and the pulsation damping device 5 are integrated with each other and external pipes connecting them are not required, the cost and the size of the whole can be reduced, and the installation space can be largely decreased. Since external pipes are not used, there is no fear that liquid leakage due to breakage of the pipes or the like occurs after a long term use. Since the pressure loss is very small, the pump capacity can be made small so that the pump itself can be miniaturized and the installation and occupation area of the pump can be decreased.
In a still further pulsation damping device of the invention, in the air discharge valve rod pulling portion 56, a sleeve 48 which has a guide hole portion 48a in a front end portion is disposed on the air supply/discharge valve control plate 28 to be juxtaposed with the air supply valve rod pressing portion 55, and a rear end portion of the air discharge valve rod 45 is slidably passed through the guide hole portion 48a of the sleeve 48 so as to be prevented from slipping off, the rear end portion having a flange 44. According to this configuration, the air discharge valve 43 can be surely pulled and opened in accordance with the movement of the air supply/discharge valve control plate 28 which is moved followingly with the contracting operation of the pulsation suppression diaphragm 18.
In a still further pulsation damping device of the invention, in the air discharge valve rod 45, a root portion with respect to the air discharge valve 43 is slidably passed through a valve rod guide hole portion 47a of an air discharge valve rod holder 47 which is disposed in the valve casing 23. According to this configuration, the linear movement guidance of the air discharge valve rod 45 can be surely performed.
In a still further pulsation damping device of the invention, the air supply valve rod 41 is slidably passed through a valve rod pass hole 39 of an air supply valve holder 40 which is disposed in the valve casing 23, the valve rod pass hole 39 being formed in a rear end portion of the air supply valve holder, and a rear end portion of the air supply valve rod 41 protrudes toward a rear side of the air supply valve holder 40. According to this configuration, the linear movement guidance of the air supply valve rod 41 can be surely performed.
In a still further pulsation damping device of the invention, a front end portion of each of the guide shafts 58 is coupled integrally with the valve casing 23, and a rear end portion of the guide shaft 58 is slidably passed through a guide sleeve 22 fixed to the air supply/discharge valve control plate 28 so as to be prevented from slipping off, the rear end portion having a flange 58a. According to this configuration, the air supply/discharge valve control plate 28 can be moved in parallel stably and surely